Hazardous Area Zone Classification — Complete Guide
Zone classification is the process of identifying and categorising areas where explosive atmospheres may occur. The zone determines the minimum level of protection required for any electrical equipment installed in that area. Getting zone classification right is fundamental to safe electrical installation and is a core topic in CompEx Ex01–Ex04.
Gas Zones
| Zone | Definition | Frequency | EPL Required |
|---|---|---|---|
| Zone 0 | Explosive atmosphere present continuously or for long periods | >1000 hrs/yr | EPL Ga |
| Zone 1 | Explosive atmosphere likely to occur in normal operation | 10–1000 hrs/yr | EPL Gb |
| Zone 2 | Explosive atmosphere unlikely in normal operation, but possible | <10 hrs/yr | EPL Gc |
Dust Zones
| Zone | Definition | EPL Required |
|---|---|---|
| Zone 20 | Combustible dust cloud continuously present | EPL Da |
| Zone 21 | Combustible dust cloud likely in normal operation | EPL Db |
| Zone 22 | Combustible dust cloud unlikely in normal operation | EPL Dc |
Who Classifies Zones?
Zone classification is carried out by a competent person — typically a process engineer or safety engineer working with the plant area classification drawings. Electricians must be able to read and interpret zone classification drawings to ensure they select and install appropriate equipment.
Never assume a zone classification without checking the drawings. Zone boundaries can change as plant layouts are modified. Always verify the current zone classification for any area where you are installing or inspecting equipment.
Zone Classification and Equipment Selection
Zone classification drives every equipment selection decision. EPL Ga equipment (Zone 0) provides the highest level of protection and can be used anywhere. EPL Gc equipment (Zone 2) provides the minimum acceptable level and can only be used in Zone 2. The most common practical scenario is selecting EPL Gb equipment for Zone 1 installations.
Reading about it is one thing. EX Academy puts you in the scenario — interactive inspection simulations, equipment selection decisions, and 1,185+ practice questions referenced to IEC 60079.
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